Technology
An output stage, which also operates in class A mode with over 6 mA of closed-circuit current, functions as a current amplifier.
The transistors and resistors utilized also had an enormous effect on the audio quality. To facilitate selection, we assem- bled several models and subjected them to extensive listening tests. All this trouble more than paid off: the final GainStation 8 op-amp has a slew rate of over 100V/µs—several times faster than industrial op-amps. This is an absolute prerequisite for clean, transparent and dynamic audio. Transients are depicted with unparalleled accuracy, resulting in an open, airy and reali- stic sound.
The clean stage is based on a fully discrete, balanced instru- ment amplifier and also operates in class A mode. The special circuit configuration ensures consistent frequency response at virtually every gain setting. With its slew rate of over 200 V/µs, it is able to amplify fast transients and extremely high frequencies with almost no distortion. An op-amp subsequently converts the instrument amplifier‘s output signal into an unbalanced signal, which is fed to the tube.
The tube type—a Sovtek® 12 AX7 LPS—was also selected after extensive measurements and listening tests. This tube type delivers an open, transparent sound, excellent noise values and is especially reliable. A generously proportioned 2.2 µF WIMA-MKP decoupling capacitor is utilized to ensure clean, punchy low frequency response. An impedance converter adapts the tube‘s high-impedance signal to the output stage, which also utilizes fully discrete op-amps and can easily drive extreme cable lengths. Coupling condensers were used as sparingly as possible to avoid their inherent disadvantages such as diffuse sound, slurring and loss of dynamics. Instead, servo circuits were utilized to eliminate DC artifacts.
